1. Field of the Invention
The present invention relates to a detecting agent for measuring dimethyl sulfide (DMS: H.sub.3 C--S--CH.sub.3, referred to as "DMS" in the present specification) contained in a fuel gas such as city gas and LP gas as an odorant or generating at a manufacturing factory and life environment easily, rapidly and precisely, and a method for preparing the same. Additionally, the present invention relates to a detecting agent tube for DMS in a gas-phase.
2. Prior Arts
City gas, LP gas and other fuel gases to be sent from a source of supply to each home by means of a pipe are sent to various combustion appliances such as a boiler burner, a gas turbine or a gas engine, a gas heater, a gas range, a gas rice cooker, an instantaneous water heater, a bath boiler and a gas stove through a pressure adjuster, a gas meter, an on-off valve and other various appliances provided on each pipe and consumed.
No matter whether they are in use or not, these fuel gases must always be kept from leaking from these pipes, various appliances and various combustion appliances. In addition, sufficient care must be taken in order to avoid danger due to imperfect combustion in various combustion appliances.
The leakage of a gas may occur not only from pipes, joints, gas meters and valves but also from various combustion appliances themselves. Hence, the leakage of a gas is observed by detecting a gas flow and measuring the flow rate, and necessary repair and control are performed on the pipe chase and gas appliances to maintain safety according to the results of the observation. One of the techniques for detecting the leakage of a gas immediately and giving warning of danger is a method of sensing leakage easily and immediately by adding an odorous compound such as mercaptan into a fuel gas.
As such an additive an odorous compound, namely, an odorant, generally, a sulfur compound such as tetrahydrothiophene (THT:C.sub.4 H.sub.8 S), tert-butyl mercaptan [TBM: C(CH.sub.3).sub.3 --SH] and DMS are employed singly or as an admixture of two or more components.
Looking at the condition of the use thereof in our country, THT is the most used, and TBM-based ones are secondarily used the secondly most. However, if it is restricted to enterprises supplying city gas with LNG as a main raw material, most of them employ a mixed odorant of TBM and DMS.
In order to measure the amount of an odorant, generally a gas chromatograph equipped with a flame photometric detector (FPD-GC method) is employed at a laboratory level. However, since the leakage of a gas occurs not only from pipe lines, joints, gas meters and valves but also from various combustion appliances themselves, the method for mesuring the odorant, rapidly and precisely in the field is keenly desired.
In this connection, in the case of the odorant being TBM, a practical use has already been realized. In the case of the odorant being THT, there exists (1) a transferable gas chromatograph [J. High Resolut. Chromatogr., 16, 379 (1993)], (2) a THT measuring machine and (3) a THT detector tube (Drager, Germany), each have its merits and demerits.
In particular, the above conventional (3) THT detector tubes require much time for measurement and besides show unclear coloring, a large readout error and insufficient results of measurement, and there exists no proper one. The present inventors have solved various problems in conventional detecting agents and have developed a THT detecting agent capable of obtaining a detecting agent exhibiting clear coloring over a short time elaborately and a THT detector tube employing the same (Japanese Patent Application No. 8-262530).
An odorant in city gas is one of the important items in the control of quality, and it needs be contained in an amount enabling the object of addition, namely, the object of warning of leakage, to be accomplished, and the presence and amount of the odorant must always be observed. Because of this, the number of traders concerned with measuring the concentration also at the end of a gas pipe line is increasing. In this connection, regarding TBM and THT, a detector tube capable of measuring the concentration at the field of the end of a gas pipe line easily has already been developed, but there exists none for DMS.
It is known that sulfides such as DMS are oxidized by potassium permanganate to produce sulfone. The present inventors manufactured as an experiment various DMS detecting agent tubes with a permanganate as a detecting reagent and examined the characteristics thereof in detail, and as a result, have found that a detecting agent obtainable by selecting quartz sand particularly as a support and depositing potassium permanganate on the quartz sand is highly sensitive to DMS in city gas. It has become apparent that, in the case of depositing only potassium permanganate on quartz sand, however, the coloring is unclear, the readout error is large and the results of measurement are insufficient. The present invention has led, on the basis of this knowledge, to the development of a detecting agent capable of measuring DMS simply, rapidly and precisely, a process for preparing the same and a detecting agent tube for DMS in a gas phase.